This invention relates to an information transmission system wherein a plurality of information processing apparatuses distributed over a wide area are connected in parallel with each other via a commonly provided information transmitting bus line, and information is arbitrarily transmitted between these information processing apparatuses.
In the case where a plurality of information processing apparatuses are distributed over a comparatively wide area so that each of the apparatuses is separated from others by comparatively long distances, interconnection of all the information processing apparatuses through separate transmission lines is not economical because such an arrangement not only requires a greater amount of transmission lines but also requires the provision of a plurality of information transmitting devices in each apparatus. To eliminate the latter disadvantage of the above described arrangement, there has been proposed an information transmitting system of the type shown in FIG. 1, wherein a plurality of information processing apparatuses, 1 through N, are connected in parallel with a common information transmitting bus line CL. Under the control of a bus line control device LC, information transmission between these apparatuses is arbitrarily carried out over the bus line CL.
However, such an information transmitting system requires a bus line control device, LC, capable of supervising and controlling the bus line against duplicate use of the bus line, and any trouble in the bus line control device, LC, tends to cause a total failure of the information transmitting system. For this reason, the bus line control device LC is made of high precision circuits operable in a multiplex manner, thus requiring a high cost of manufacture.